Refrigerating system with low temperature stabilization



y 1955 R. c. WEBBER REFRIGERATING SYSTEM WITH LOW TEMPERATURE STABILIZATIQN Filed Oct. 15. 195:5

2 Sheets-Sheet 1 IN VEN TOR. Fawn CC M5525,-

' ag/42414 AF'Y'OF/VZ'K' May 31, 1955 R. c. WEBBER REFRIGERATING SYSTEM WITH LOW TEMPERATURE STABILIZATION 2 Sheets-Sheet 2 Filed Oct. 13, 1953 gag/Iv INVENTOR. fibaz'fi'r (Ia/Ewan? BY.

United tates Paten .REFRIGERATING SYSTEM WITH LBW TEMPERA- TURE STABILIZATION RobertC. vvebben'lntlianapolis, ind. 7 .Application October 13,1953, Serial No. 385,801

7 Claims. (Cl. 62-3) This application; relates to an improvement over my co-pending application" for LoweTemperature, Stabilized Refrigerating System, Serial .No. 297,486, filed July 7, 1952, and is concerned with. low-temperature refrigerating systems and particularly with means for stabilizing such systems.

In my prior application, I provided what I'believed to'be a'complete solution .tothe problem of insuring the contemplated operation of a thermo-responsive expansion valve where the (system was being operated to maintain the evaporator at temperatures below the boilingpoint of the control fluid in the thermo-responsive valve,

such fluid being in heat-exchanging relation Withthe refrigerantflowing from the. evaporator. While my. invert tion disclosed therein has greatly improved the operation ofsuch asystem, I havefound that during relatively long periods'when'the compressoris not'running, my system for supplying heat to the control fluid is,lthereby, in-

activated and the fluid will liquefy, resulting in alloss ofcontrol over the .system-thevery thing which the invention of my prior application was designed to guard against.

The primary object of this invention is,'.'therefore, to provide means, foruse in cooperation with the invention of'my prior application, for insuring againsfliquefaction of the control fluid in the expansion valve. during those periods when the'compressor is not running and, *to this end, to provide means for supplyingsomeheat "to the control fluid during such periods.

Further objects will become apparent 'asthedescrip- 'tion proceeds.

To the accomplishment of the above andr'elated ob- 'jects, my invention'may beembodied in the form'illus- 'trated in the accompanying drawings, attention being called to the fact, however, that thedrawings are illusitrativeonly, and-that change may be made in the'specific construction illustrated and described, so long 'asthe scope of the appended claims is not violated.

Fig. 1' is a diagrammaticillustration of arefrigera'tiou system embodying my invention; and

Fig. 2 is a vertical sectional view, upon an enlarged scale, through one form of thermo-responsive expansion valve-modified for use with the present invention.

Referring more particularly to the drawings, I have 'shown a compressor 10 connected by a conduit 11 to a #condenserlZ, preferably through an oil separator '13.

A conduit 14 connects the condenser'to a receiver "15 in turn connected to an expansion'valve 16 by'means of a conduit 17. A conduit '18 connects the expansion valve to an evaporator19connected to the low pressure si'de'of the compressor 10 through a 'conduit20.

In Fig. 2, I have illustrated one type of expansion valve conventionally used in such a system comprising a body 21'providing'a chamber-24 having an inlet passage 22, to which the conduit 17 is connected, and an outlet passage 23,to"which the conduit 18is connected. A

valve port 25 guards the entrance :of passage 22'into chamber 24 and is controlled by a movable valve needle trol fluid in bellows 31 the temperature'of the'refrigeran't,

prevent liquefaction of the control fluid.

Zfififiifl Patented May 31, 1955 ice '26. A bellows 27 is open on one endto chamber 24 and carries a'bell 28 at theopposite end mechanically connected through yoke'29 to the valve needle 26 whereby the movement of the valve needle is placed partially .under the influence of the'refrigerant pressure inchamber 24.

Adjacent to, but separated from, chamber 24 .is a further chamber 3%) in which is supported a further bellows 31 having a movable'walldl. A'stem33,tcarrie'd .by this movablewall, abuts'a stem '34, carried by the bell 28 in bellows 27, whereby the valve" needle 26 is "placed, also, under the controliof the -movements of'the movable wall '32 of bellows 31.

A feeler bulb 35 is placed in heat-exchanging'relation with'the" refrigerant flowing'from the evaporator 19by .fluids Jcustomarily'used'in the bellows 31 'andbulb 35. In the system in which my invention is designed primarily for use, the temperatures desired to be attained .range far below the boiling-points of such'fluids. Since the fluid inithe'system, including the bellows 31.and"the bulb '35, is intended" tobe placed indirect heat exchange relation with'the refrigerant as it flows fromsuchan extremely cold evaporator, it very often happens thatthe "fluid will becooledbelow its boiling-point "and become liquefied. When this occurs, control .of the expansion valve is completely destroyed, since such control depends'upon the maintenance of a gaseous fluid in bellows 31.

In order to insure against such liquefaction of the control fluid, I presented, in my co-pending application identified above, a scheme 'for impressing upon'theconflowing fromthe receiver toward the expansion valve, which is ordinarily maintained at substantiallyroom' temperature. 'I accomplished this'by coiling a portion 37 of'the conduit 17 about the valve body 21in the region occupied by bellows '31. "Thereby, heat 'from therefr igerant was supplied tothecontrol'fiuid at a ratedependent upon the load demands on the evaporator.

Where the heat-loss from the evaporator is comparatively rapid so that the periods during which the compressor is not running (or in which the expansion valve is completely closed) are of comparatively "shortduration, such an expedienthas proven-quite"satisfactory to However, where such heat-loss is so small as toresult in periods of relatively long duration during which the compressor is not running, the condition commonly referred to as frost-back will occur. When that happens, the conduit 20 leading'from the evaporator will, give up itsheat to the evaporator and in turn' become cooled to a tem- .perature below .the boiling-point of the control fluid in bulb 35. 'Very shortly thereafter, the fluid in the 'entiresystem including the bellows 31 will become all or partially liquefied and complete loss of control of t the expansion valve will result.

"By my present invention, 1 have-eliminated the possibility of the occurrence of such a mishap. I'have done so by providing means 'for'insuring a continuous, though somewhat reduced, flow of refrigerant through the coiled portion 37 of conduit 17. Even duringperiods when the compressor is shut down, the refrigerant is maintained in the system, between the receiver'andthc expansion valve, at a relatively high pressure. A oneway valve is conventionally provided on the inlet side of the receiver to prevent the loss of this pressure back towards the compressor, and the expansion valve itself, being closed during most of the time when the compressor is not running, prevents pressure loss in the direction of the evaporator.

I have found, therefore, that by providing a by-pas-s around the expansion valve to permit a constant, though somewhat reduced, flow of refrigerant through coils 37, sutiicient heat will be transferred, from the slowly flowing refrigerant to the control fluid in bellows 31, to prevent liquefaction of the fluid.

I have illustrated such a by-pass in the form of a small tube 38, connected at one end to the conduit 17, between the coiled portion 37 thereof and the inlet passage 22 of valve body 21, and at the other end to the conduit 18 ahead of evaporator 19. It will be obvious, that the last-mentioned end of tube 38 could also be connected into conduit 20 at the outlet end of evaporator 19, but

it will also be obvious that to do so would reduce the efficiency of the system since that portion of the refrigerant passing through the by-pass 38 would not pass through the evaporator. The illustrated form is, therefore, considered to be the optimum arrangement.

I have found that the optimum size of tube to use for bypass 38 is one having an internal diameter of approximately ,{;4 inch for those systems using compressors having a rating of one horse power or less, and an internal diameter of %4 inch multiplied by the compressor rating for those systems using compressors having ratings greater than one horse power. By-pass diameters substantially less than these sizes will not pass suflicient refrigerant to prevent the occurrence of liquefaction of the control fluid; while by-pass diameters substantially greater than the stated sizes will materially reduce the efiiciency of the system.

While I have illustrated and described my concept for providing for a continuous, though diminutive, flow of refrigerant through the coil 37 during periods when the compressor is not running, in the form of the by-pass tube 38, it will, I believe, be apparent to those skilled in the art, in light of this disclosure, that other, though perhaps less statisfactory, expedients for maintaining such continuous flow, could be provided, and it is not intended that the claims herein should be construed to limit my concept precisely to the construction illustrated. One such expedient could be, in the form of expansion valve here illustrated, the provision of a very small passage; such as shown at 40 in Fig. 2, for permitting a continuous, though relatively small flow of refrigerant from the inlet passage 22 into chamber 24, even when the valve needle 26 is solidly seated to close the port 25.

I claim:

1. A system of the class described comprising a compressor, a condenser, a first conduit means connecting said compressor to said condenser, an expansion valve, a second conduit means connecting said condenser to said expansion valve, an evaporator, a third conduit means connecting said expansion valve to said compressor 'through said evaporator, thermo-responsive means for actuating said expansion valve comprising means providing a chamber having a movable wall, means connecting said movable wall to actuate said valve, and a feeler bulb arranged in heat-exchanging relation with the refrigerant flowing from said evaporator, the interiors of said bulb and said chamber being in communication and filled with an expansible fluid, and means for preventing liquefaction of said expansible fluid comprising means providing a heat-exchanging relation between the refrigerant flowing in said second conduit and the fluid in said chamber, and means providing for a diminutive flow of refrigerant through the last-named means to said fourth conduit means during periods when said expansion valve is closed.

2. In a system of the class described, a compressor, a condenser, a first conduit means connecting said compressor to said condenser, a receiver, a second conduit means connecting said condenser to said receiver, an expansion "alve, a third conduit means connecting said receiver to said expansion valve, an evaporator, a fourth conduit means connecting said expansion valve to said evaporator, a fifth conduit means connecting said evaporator to said compressor, thermo-responsive means for controlling said expansion valve comprising means proiding an expansible chamberhaving a movable wall, means operatively connecting said movable wall to actuate said valve, a feeler bulb mounted in heat-exchanging relation with the refrigerant in said fifth conduit means, and means providing communication between the interior of said bulb and the interior of said chamber, said bulb, said communication establishing means and said chamber being filled with an expansible fluid, a portion of said third conduit means being arranged in heat-exchanging relation with the fluid in said chamber, and means for maintaining a diminutive flow of refrigerant through said portion of said third conduit means during periods when said compressor is not running comprising means providing an uninterrupted, but restricted flow-path for refrigerant, flowing from said portion of said third conduit means, from the side of said expansion valve to which said third conduit means is connected, to the side of said valve to which said fourth conduit means is connected.

3. The system of claim 2 in which the last-named means comprises a tube of relatively small diameter connected between said third conduit means and said fourth conduit means to form a by-pass around said expansion valve.

4. The system of claim 3 in which said tube has an internal diameter equal to substantially ,4;4 inch for systems using compressors having a rating of one horsepower or less, and an internal diameter equal to substantially %4 inch multiplied by the horse-power rating of the compressor for systems using compressors having a rating greater than one horsepower.

5. In a low temperature refrigerating system, a compressor, a condenser, a first conduit means connecting said compressor to said condenser, a receiver, a second conduit means connecting said condenser to said receiver, an expansion valve, a third conduit means connecting said receiver to said expansion valve, an evaporator, a fourth conduit means connecting said expan sion valve to said evaporator, a fifth conduit means connecting said evaporator to said compressor, thermoresponsive means for controlling said expansion valve comprising means providing a variable-volume chamber having a movable wall, a feeler bulb arranged in heat-exchanging relation with said fifth conduit means, means providing communication between the interior of said bulb and the interior of said chamber, said bulb, said communication providing means and said chamber being filled with an expansible fluid having a boiling point below normal atmospheric temperatures but above the temperature desired to be attained at said evaporator, and means operatively connecting said 'valve to move in response to movements of said movable wall, and means for maintaining the fluid in said chamber above its boiling point comprising means establishing a heat-exchanging relation between a portion of said third conduit means and said chamber, and a tube of relatively small internal diameter connected to said third conduit means, at a point between said portion thereof and said expansion valve, said tube further being connected to said fourth conduit means to maintain a diminutive flow of refrigerant through said portion during periods when said expansion valve is closed.

6. Ina refrigerating system which includes a thermostatically-controlled expansion valve controlling refrigerant fiow from the receiver to the evaporator, said valve being dominated by an expansible fluid subject to the temperatures of the refrigerant flowing from the evaporator toward the compressor and acting upon a movable wall mechanically connected to move said valve, and means arranged to impress upon the fluid in said chamber the temperature of the refrigerant flowing from said receiver toward said expansion valve, the invention of means for maintaining a diminutive flow of refrigerant through the last-named means during times when said expansion valve is in its fully closed position, such means comprising means providing a by-pass for the refrigerant around said expansion valve.

7. The system of claim 6 in which said means providing said by-pass comprises a tube connected across the inlet and outlet sides of said expansion valve to permit a diminutive fiow of refrigerant therethrough References Cited in the file of this patent UNITED STATES PATENTS 2,077,865 Wile Apr. 20, 1937 2,205,166 Dube June 18, 1940 2,337,862 Baer Dec. 28, 1943 2,351,140 McCloy June 13, 1944 2,463,892 Martin Mar. 8, 1949 2,471,448 Platon May 31, 1949 2,667,757 Shoemaker Feb. 2, 1954 2,675,683 McGrath Apr. 20, 1954 

